In an interview from prison, Ahmed has now accused MI5 of offering him money or a reduced sentence in return for withdrawing his complaint when he appeals his conviction this year.

He claims that he was visited in Manchester prison by two men, one of whom identified himself as a MI5 officer and the other as a police officer.

"They said they wanted my advice about tackling extremism and then said they could offer me protection if I helped them," he said.

"Then they said, 'If you withdraw what you are saying about torture, we can make a deal with you to reduce your sentence, or if you want to take money we can give you money.' "

Ahmed's solicitor has written to the Crown Prosecution Service to condemn the approach, saying it amounted to "an attempt to pervert the course of justice".

A spokesman for the Home Office said: "We don't comment on matters of security. Security service officers act within the law."

Ahmed was arrested in Pakistan in 2006 and subjected to interrogation by the country's infamous Inter-Services Intelligence before being deported to Britain in 2007.

The judge at his trial said that Ahmed should serve a minimum of 10 years before he is considered for parole.

MI5 and MI6 have come under increased scrutiny for failing to prevent the alleged torture of terrorism suspects in foreign prisons.

Dozens of British citizens and residents claim they suffered abuse in countries including Afghanistan, Pakistan, Egypt, Syria, Jordan, Morocco, the United Arab Emirates and Kenya with the knowledge of British agents.

In March the Attorney General launched a police investigation into the alleged collusion of MI5 in the treatment of Binyam Mohamed, the former Guantanamo Bay prisoner.